There is a need for solvent-free, low viscosity, hot melt adhesive (HMA) and pressure sensitive adhesive (PSA) formulations, that maintain adhesive strength at high use temperatures (e.g., 104° F. (40° C.) and above).
U.S. Pat. No. 5,705,565 discloses relatively high molecular weight substantially linear ethylene polymers, for example, polyethylenes prepared by constrained geometry catalysis, which are grafted with one or more unsaturated organic compounds containing both ethylenic unsaturation and a carbonyl group, for example, maleic anhydride. These graft-modified substantially linear ethylene polymers impart desirable compatibility and impact properties to various thermoplastic polymer blends, and have adhesive properties.
U.S. Pat. No. 4,927,888 (see also U.S. Pat. No. 4,966,810 and U.S. Pat. No. 4,762,890) discloses maleic anhydride grafting reactions to polymers, at low pressures, by feeding the polymer through a multiple screw extruder, and injecting the maleic anhydride and a free radical initiator into the extruder. The maleic anhydride and initiator can be pre-mixed in a solvent solution. Between 0.75 and 2.0 weight percent of the graft copolymer comprises maleic anhydride. The graft copolymer can further be blended with an olefinic polymer to yield an adhesive thermoplastics suitable for use as food packaging multilayer coextruded films.
International Publication No. WO 98/38245 discloses a polyethylene composition comprising from 5 to 70 weight percent of a homogeneous ethylene/α-olefin interpolymer, from 30 to 95 weight percent of at least one filler, and from 0.1 weight percent to less than 10 weight percent of at least one functionalized polyethylene. Maleic anhydride grafted polyethylenes of relatively high molecular weights are used in the experimental examples.
International Publication No. WO 2005/100501 discloses an article comprising: 1) a functionalized component, 2) tackifier, and 3) an olefin polymer, comprising one or more C3 to C40 olefins, optionally one or more diolefins, and less than 5 mole of ethylene, and having a Dot T-Peel of one Newton or more, a branching index (g′) of 0.95 or less, measured at the Mz of the polymer; and an Mw of 100,000 or less. The functional component is selected from the group consisting of functionalized polymers, functionalized oligomers and beta nucleating agents (see abstract).
International Publication No. WO 97/22471 (see also EP0873242B1) discloses a process for preparing a laminate comprising a first substrate (I) and a second substrate (II), which comprises an ethylene or propylene polymer, and which is bonded to the first substrate by means of a polymeric adhesive. The process comprises the steps of: A) applying to the first substrate (I) a primer comprising an organic solvent and an ethylene or propylene polymer, having grafted thereto, an unsaturated carboxylic acid or an anhydride, ester, amide, imide or metal salt thereof, and B) injection molding an ethylene or propylene polymer and optional additives onto the primed substrate (I).
International Publication No. WO 2004/035680 discloses highly filled polymer compositions comprising a low molecular weight ethylene and/or alpha olefin homopolymers and copolymers, or blends therefrom, filled with high concentrations of fillers or additives. Examples of such fillers or additives include fire retardants, talc, ceramic manufacturing agents, color concentrates, crosslinking agents, and blowing agents.
U.S. Pat. No. 5,066,542 discloses succinic acid or succinic anhydride grafts of HDPE, which are blended with LLDPE, for example, ethylene/1-octene copolymers, to form blends having useful adhesive properties at elevated temperatures. The succinic acid or succinic anhydride groups are provided by grafting, respectively, maleic acid or maleic anhydride onto the HDPE.
U.S. Pat. No. 4,039,560 discloses a method for producing a modified waxy ethylene polymer, which comprises: (a) polymerizing ethylene in an inert hydrocarbon solvent at 120° C.-250° C., and pressure ranging from the vapor pressure of the solvent at the polymerization temperature to 100 kg/cm2, and using a catalyst composed of a halogen compound of titanium and/or vanadium to form a waxy ethylene polymer having a viscosity average molecular weight of 500 to 30000; (b) reacting an unsaturated polycarboxylic acid with the resulting waxy ethylene polymer in the presence of a peroxide at a temperature above the melting point of the waxy ethylene polymer and up to 250° C., and if desired, (c) contacting the ethylene polymer, before, or after, the reaction with the unsaturated polycarboxylic acid, with oxygen or a gas containing oxygen. Relatively high density polyethylenes are functionalized in the experimental examples.
U.S. Pat. No. 5,045,401 discloses multicomponent thermoplastic resin blends, which have a nonisothermal crystallization half life of less than thirty seconds. Especially preferred are three component resin blends comprising a maleic anhydride grafted HDPE of relatively high molecular weight, an unmodified LLDPE copolymer having a density between about 0.905 and 0.93 g/cc, and an unmodified LLDPE copolymer having a density between about 0.89 and 0.92 g/cc. These thermoplastic resin blends can be used as the adhesive layer in multilayer structures.
International Publication No. WO 03/087178 discloses an article of manufacture comprising a copolymer of ethylene and vinyl aromatic monomer having a molecular weight of less than 15,000. Preferably, the copolymer is characterized by a backbone having a first and second terminal end group, the first terminal end group is a methyl group, the second terminal end group is a vinyl group, and wherein the ratio of the terminal methyl group to the terminal vinyl group is 0.8:1 to 1:0.8. The article of manufacture includes, but is not limited to, waxes and lubricants.
U.S. Pat. No. 6,414,102 discloses polyolefin copolymers (I) and graft copolymers (II), which are prepared from the copolymers (I). The copolymers (I) are linear copolymers containing divinylbenzene comonomer units selected from the group consisting of 1,4-divinylbenzene units, mixtures of 1,4- and 1,3-divinylbenzene units, and mixtures of 1,4-, 1,3- and 1,2-divinylbenzene units. This patent discloses grafting reactions with styrene, p-methylstyrene and methylmethacrylate.
U.S. Pat. No. 6,299,985 discloses polyethylene-based adhesive compositions which contain as little as 5 weight percent, and up to 35 weight percent, of an acid-grafted metallocene polyethylene. The compositions are disclosed as having superior peel strength to comparable compositions containing an acid grafted non-metallocene and EVA or EMA polyethylene. Compositions containing an acid-grafted metallocene polyethylene component, based on a relatively high molecular weight metallocene polyethylene having a melt-flow ratio of less than 6.53, and an Mw/Mn of greater than the melt flow ratio less 4.63, can be used as an adhesive.
International Publication No. WO2007/008765 discloses compositions containing at least one silane-grafted polyolefin, and in particular, to compositions containing at least one silane-grafted ethylene/α-olefin polymer, which has a melt viscosity less than 50,000 cP, and adhesives containing the same. In one embodiment, the at least one silane-grafted ethylene/α-olefin polymer is formed from an ethylene/α-olefin polymer that has a molecular weight distribution from 1 to 3.5. The invention also relates to the preparation of the silane-grafted polymers, by reacting, for example, an ethylene/α-olefin polymer with at least one silane compound and at least one initiator.
International Publication No. WO 2006/069205 discloses an adhesive composition comprising a copolymer of propylene and at least one comonomer, selected from the group consisting of ethylene and C4-20 α-olefins. The copolymer has the following properties: (i) a content of units derived from propylene of greater than about 50 mole percent, (ii) a Brookfield viscosity at 190° C. from about 50 to about 100,000 cP, (iii) an MWD from about 1.5 to about 15, and (iv) a residual catalyst metal content less than about 50 ppm. The propylene copolymer may be functionalized with one or more compounds, including maleic anhydride.
International Publication No. WO 02/36651 discloses propylene ethylene copolymers with an ethylene content between 8 and 32 mole percent, and which have been grafted with maleic anhydride and a peroxide. The functionality level is higher than what is reported with polypropylene. Relatively high molecular weight polypropylenes are functionalized in the experimental examples.
Preparation and Characterization of Functionalized Polyethylene Waxes, Zhang et al., Suliao Gongye (2003), 31 (2), 13-15, 18 (Abstract), discloses the functionalization of polyethylene waxes by grafting maleic anhydride or maleic anhydride-styrene onto polyethylene waxes.
European Patent EP 0 850 138B1 discloses a laminate comprising: a) a first substrate comprising a first substantially linear olefin copolymer; b) an adhesion promoter, which comprises a “polar group functionalized” second substantially linear olefin copolymer; c) a tackifying resin admixed with the adhesion promoter, or an adhesive superposing the adhesion promoter or admixed therewith; and d) a second substrate adhesively bonded to the first substrate. Relatively high molecular weight functionalized ethylene-based polymers are used in the experimental examples.
International Publication No. WO 2004/031292 discloses a thermoplastic composition that comprises: (i) from 1 to 99 percent, by weight of the total composition, of at least one thermoplastic copolymer, for example, styrene block copolymers, and (ii) from 1 to 99 percent, by weight of the total composition, of at least one homogeneously branched ethylene/α-olefin interpolymer, for example ethylene/1-octene, having a density of less than, or equal to, 0.899 g/cc, and a Brookfield viscosity of greater than 500 cP (350° F.).
U.S. Pat. No. 6,335,410 (see also U.S. Pat. Nos. 6,054,544 and 6,723,810) discloses a non-pourable homogeneous ultra-low molecular weight ethylene polymer composition, and a process for the preparation thereof. Such polymer compositions have longer lamella and a greater degree of crystalline organization, than corresponding higher molecular weight materials at an equivalent density.
International Publication No. WO 2005/111145 discloses propylene compositions comprising a propylene polymer, a substantially linear ethylene polymer, linear ethylene polymer or combinations thereof, a low molecular weight polymer, and optionally a filler. The compositions have improved processability, with a good balance of stiffness and toughness, and demonstrate improved scratch resistance in injection molded articles. The propylene polymer may be graft modified.
Additional functionalized polyolefins and/or polyolefins are disclosed in U.S. Publication Nos. 2005/0043455 and 2003/0114322; U.S. Pat. No. 5,824,718 (see also related U.S. Pat. Nos. 5,741,852; 6,048,935; 4,806,594); 5,994,474; 6,043,401; 5,498,809; 5,266,627; 6,395,791 (see also 6,583,222; and 6,585,188); 6,172,015; International Application Nos. WO03/040201 and WO90/01503; and European Patent 0944670B1.
There remains a need for low viscosity, low density, functionalized polyolefins that can be used in solvent-free, low viscosity adhesive formulations. There is a further need for improved adhesives for the following applications: case and carton sealing, automotive, graphic arts, nonwovens, panel assembly, high performance tapes, contact hot melt adhesives, paperboard coatings, inks, personal care and cosmetic products, sealants, color and additive concentrates, carpet-tape adhesives, and woodworking applications.
Currently, some of the high performance pressure sensitive adhesives (PSA) based on high molecular weight (MW) styrene block copolymers (SBCs) can only be produced using solvents. They can not be applied from a hot melt, due to their high viscosity (high molecular weight). The trend is to use solvent-free adhesives for both environmental and cost reasons. Also, reactive hot melts, based on urethane chemistry are expensive, and have safety issues, since they utilize isocyanate chemistry. Thus, there is a need for solvent-free compositions that are safe and cost-effective to produce, and that can be used as adhesives and in other applications (for example, applications that require compositions with improved paintability, toughness, compatibilization, impact resistance and/or flexibility).
At least some of these issues and others have been satisfied by the following invention.